Research Progress in Area 1 方向 ( 一 ) 課題進展 83 Abstract Phosphorus availability limits phytoplankton production in some regions of the oceans. Bacteria use the ABC-type phosphate transporter for phosphate acquisition, which comprises the periplasmic high-affinity phosphatebinding protein PstS. Cyanophage was able to upregulate phosphate uptake of the infected host cyanobacterial under P-limited conditions with unknown molecular mechanism. In this proposal, Prof. Dang would like to study adaptation mechanismof cyanophage to phosphate limitation by regulating phosphate uptake through 1) elucidating phylogeny and geographic distribution of cyanophage PstS genes; 2) determining phosphate-binding affinities of cyanophage PstS proteins; 3) making a structural comparison of cyanophagePstSproteins; 4) determining complex structure of host PstCAB with cyanophage PstS protein bound; and 5) exploring the role of phage gp247 in phosphate uptake during infection. Research Activities and Progress • Successfully purified PstCAB complex and PstS protein for structural and biochemical studies; • Determined structures of PstCAB complex in different states using single particle cryo-EM; • 3D structural prediction suggested gp247 function as a porin protein and plays important roles in phosphate acquisition during infection. Key Findings • For the first time, the structure of PstCAB complex was determined at near-atomic resolution, allowing them to generate protein models for further analysis; • Interaction between PstS and PstCAB is weak, and the PstSCAB complex is disassembled during purification; • PstCAB complex contains one PstC, one PstA, and two PstB subunits. The architecture is similar to other ABC transporters; • The putative phosphate binding site in PstCAB complex has been identified; • Structural comparison of PstCAB under different sates enabled depiction its working mechanism; • Functional assay confirmed identified key residues in phosphate transport. Research Output Publication 0 Trained personnel 14 Adaptation of Cyanophages to Phosphate Limitation by Regulating Activity of Phosphate-Specific Transporter of Cyanobacteria Host Prof. Shangyu Dang The Hong Kong University of Science and Technology Fig 1. Phosphate binding site of PstCAB
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